The present invention is directed to an improvement in a cooling arrangement for a dental instrument which has a tool, for example rotating, oscillating or a laser for mechanically removing hard dental substances.
When treating teeth, particularly given mechanical erosion of hard dental substances with an active tool, such as, for example, rotating, oscillating tools or lasers, it is necessary to adequately cool the preparation location in order to avoid heat damage. At least in the case of all rotating instruments, this cooling currently usually occurs by supplying a water/air mixture as a spray. Examples of these arrangements are disclosed in German DE 23 55 961 and Soviet Union 715009. The spray is thereby produced in one or more nozzles in the head housing of the instrument, wherein a relatively small volume stream of water and a volume stream of air that is far greater in comparison to that of the water, are mixed with one another. The ratio of the volume stream of air to water amounts to approximately 100:1. During a preparation, the air added to the cooling water in this way in a relatively great quantity carries the spray cloud out of the patient's mouth into the adjacent environment as an aerosol. Since the water emerging from the dental unit can already be contaminated with germs and the spray flow is contaminated by entrained germs in the mouth, there is a risk of infecting the environment of the work field with germs and, thus, a risk of a direct burden for the treating personnel and for the following patients as well.
Earlier attempts to cool the tool and the preparation location with a water jet directed onto the tool have been abandoned. It was apparently extremely difficult to direct the water jet exactly onto the preparation location, particularly to direct it thereonto over a duration, taking potential calcification or blockage of the extremely small nozzle opening at the water exit location into consideration. Another reason was that an air pillow is formed around the rapidly rotating tool and the water jet is deflected by this air pillow so that it was not possible to optimally hit and, thus, cool the tool or the preparation location, as well. Cooling by water jet is also disadvantageous insofar as the water jet can rebound at a tooth surface and, thus, strike the attending person.